1. Field of the Invention
This invention relates to processes for the preparation of heterocyclic compounds. More specifically, this invention relates to the synthesis of compounds that can be used to prepare pharmaceutical agents such as benzimidazole derivatives. This invention further includes intermediate compounds obtained during the synthesis of the heterocyclic compounds according to this invention and to the methods of preparation thereof.
2. Description of the State of the Art
Benzimidazole derivatives have been investigated as therapeutics for treating cancers, viral infections, and diseases and pathological conditions involving inflammation and have been disclosed in a number of patents and publications in the last several years, including U.S. Patent Publication Nos. 2003/0232869, 2004/0116710, and 2003/0216460; U.S. Pat. No. 5,525,625; WO 98/43960; WO 99/01421; WO 99/01426; WO 00/41505; WO 00/42002; WO 00/42003; WO 00/41994; WO 00/42022; WO 00/42029; WO 00/68201; WO 01/68619; WO 02/06213; WO 03/077914; and WO 03/077855.
In particular, WO 03/077914 describes the synthesis of the sodium salt of a benzimidazole derivative 11 from 2,3,4-trifluorobenzoic acid in 11 linear steps as illustrated in Scheme 1. This route is not only very long in terms of the number of steps, but also includes a number of chemical transformations that could be hazardous to carry out on a manufacturing scale, and/or produce levels of by-products that would not be acceptable in a final active pharmaceutical ingredient (API). It will be appreciated by those skilled in the art that for a process to be suitable for industrial application it should be (i) amenable to being performed on large scale, (ii) have minimal environmental impact (for example in terms of amount of raw materials required and/or the amount of waste produced), (iii) safe (for example, use materials of low toxicity that do not produce toxic waste), and (iv) as low in cost as possible (for example, by being a higher yielding and more convergent synthesis). Since heterocyclic compounds such as benzimidazoles are potentially useful as therapeutics, there is an on-going need for a more efficient synthetic route for the production of benzimidazole derivatives that is more amenable to or suitable for large-scale manufacture.
